Fine Crystalline Boehmite Preparation via Acid-Treated Inoculant
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Solution Overview
Problem
Current methods for producing boehmite for use in flame retardants in plastics fail to achieve a finely crystalline structure with a small surface area and pore volume, making it difficult to achieve high flame retardancy and mechanical strength simultaneously.
Innovation Solution
A process involving autocatalytic, hydrothermal crystallization using a specially prepared inoculator, where aluminum monohydrate is ground in an acidic aqueous dispersion to produce a boehmite with a controlled BET surface area and pore volume, resulting in a finely crystalline boehmite with a grain diameter of 50-400 nm and a BET surface area of 10-40 m^2/g.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to produce boehmite for flame retardants, then the production process is simple, but the boehmite cannot achieve a finely crystalline structure with small surface area and pore volume
Solution Approach 1:
The invention applies preliminary action by preparing a specially treated inoculator before the main crystallization process. The inoculator is ground in an acidic aqueous dispersion to reduce its surface area and pore volume before being introduced to the aluminum trihydrate slurry. This preliminary treatment of the inoculator ensures that the resulting boehmite crystals inherit the fine structure and low surface area characteristics, solving the contradiction between crystalline fineness and process complexity.
Solution Approach 2:
The invention utilizes parameter changes by controlling the pH value of the acidic aqueous dispersion during inoculator preparation, maintaining it between 2-4. This specific pH range optimizes the surface treatment of the inoculator particles, preventing excessive surface area increase while enabling effective crystallization. The parameter control of pH, along with temperature (50-70°C) and grinding time, achieves the desired fine crystalline structure with low surface area.
2Reliability
If the boehmite grain size is reduced to increase flame retardancy, then the flame retardancy class improves, but the mechanical strength of the plastic decreases
Solution Approach 1:
The invention resolves this contradiction through parameter changes by controlling the grain size within an optimal range (50-400 nm, preferably 100-300 nm) rather than minimizing it indefinitely. This specific size range, achieved through controlled crystallization using the pre-treated inoculator, provides sufficient flame retardancy while maintaining adequate mechanical strength. The D50 grain diameter control, combined with low surface area (10-40 m²/g) and low pore volume, creates a balance between flame safety and mechanical properties.
Solution Approach 2:
The invention applies composite material principles by creating a boehmite with a specific composite structure: fine grains (50-400 nm) combined with low surface area and low pore volume. This unique composite structure, achieved through the acidic dispersion treatment of the inoculator followed by controlled hydrothermal crystallization, provides both excellent flame retardancy and preserved mechanical strength, as the low surface area and pore volume prevent excessive disruption of the plastic matrix.
3Ease of operation
If the boehmite surface area is increased to improve dispersibility, then the ease of mixing improves, but the flame retardancy class decreases
Solution Approach 1:
The invention resolves this contradiction through parameter changes by optimizing the surface area to a specific range (10-40 m²/g) rather than maximizing it. This moderate surface area, achieved through controlled crystallization with pre-treated inoculator, provides sufficient dispersibility for easy mixing while maintaining the flame retardancy required for high flame retardancy class. The key is that the surface area is kept low compared to conventional boehmites, preventing the trade-off between dispersibility and flame safety.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process effectively produces boehmite with a small surface area and pore volume, enabling high flame retardancy and mechanical strength, allowing for easy mixing into plastics and achieving a high flammability class while maintaining excellent mechanical properties.
Implementation Method 1
a) an alkaline aqueous dispersion, comprising a hydrate source (Al(OH)3) and the inoculant according to one of claims 1-6, is subjected to autocatalytic, hydrothermal crystallization
Implementation Method 2
The properties of the inoculator and methods for its production are described below. An aluminum monohydrate source is used to produce the inoculator. The aluminum monohydrate source (AlO(OH)) has a boehmitic crystal structure and suitably has particle sizes with a D 50 of approximately 500 nanometers and larger and a BET surface area of 20 m 2
Data Source
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AI summary
The invention relates to a boehmite characterized by a mean grain diameter D50 in the range of 50 to 400 nm, a BET surface area in the range of 10 to 40 m²/g, and a pore volume in the range of 0.05 to 0.5 cm³/g. This boehmite is produced by starting an aqueous, alkaline dispersion containing a hydrate source and an inoculant, heating the dispersion in an autoclave to a temperature in the range of 110 to 180°C until the hydrate source is substantially consumed, and drying the resulting product. An aqueous dispersion of an aluminum monohydrate source with a boehmitic crystal structure is used to produce the inoculant. The dispersion is then milled at a pH in the range of 2 to 4.